Modifier templates does not apply

### Input code or something about issue background

https://goo.gl/Xm3cWQ

```js
block('a').def()('NO');
block('a').mods()({m: true});
block('a').mod('m').def()('YES');
```

Feels like it's too late but looks like a bug or useless sugar and we should fix that (modifier templates should apply).

### Expected Behavior

`'YES'`

### Actual Behavior

`'NO'`

### Possible Solution

Apply mods/addMods BEFORE def mode?

### Your Environment

latest bem-xjst

cc @Yeti-or @awinogradov

Start by reproducing the JavaScript snippet from the issue and tracing how modifier templates are processed relative to the default mode. The change is complete when the example produces 'YES' instead of 'NO' and the behavior is covered by an appropriate regression check.

Written by the indexing model from the issue text.